In addition to template expansion (`{{ param }}`), custom parameters defined in the Repository CR are available as CEL variables in the `on-cel-expression` annotation. This allows you to control which PipelineRuns are triggered based on repository-specific configuration. For example, with this Repository CR configuration: ```yaml apiVersion: pipelinesascode.tekton.dev/v1alpha1 kind: Repository metadata:   name: my-repo spec:   url: " https://github.com/owner/repo "   params:     - name: enable_ci       value: "true"     - name: environment       value: "staging" ``` You can use these parameters directly in your PipelineRun's CEL expression: ```yaml apiVersion: tekton.dev/v1 kind: PipelineRun metadata:   name: my-pipeline   annotations:     pipelinesascode.tekton.dev/on-cel-expression: |       event == "push" && enable_ci == "true" && environment == "staging" spec:   # ... pipeline spec ``` f you define a custom parameter with the same name as a standard CEL variable, the standard variable will take precedence in CEL expressions. Custom parameters should use unique names that don't conflict with built-in variables. `event_type` is also available as a PAC standard variable for cel evaluation.